Datasheet

PCA9570 All information provided in this document is subject to legal disclaimers. © NXP Semiconductors N.V. 2014. All rights reserved.
Product data sheet Rev. 4 — 17 September 2014 9 of 32
NXP Semiconductors
PCA9570
Remote 4-bit general purpose outputs for 1 MHz I
2
C-bus
8.3 Reading from a port (Input mode)
All ports are outputs and cannot be used as inputs. When reading the device, the data
returned is the port state at the pin. To read, the master (microcontroller) first addresses
the slave device by setting the last bit of the byte containing the slave address to logic 1.
The data byte that follows on the SDA is the value of the ports pins. There is no limit to the
number of bytes read, and the state of the output port pins is updated at each
acknowledge cycle. Logic 1 means that the port is HIGH. Logic 0 means that the port is
LOW. When the PCA9570 is read, P7 through P4 return logic ‘1’.
8.4 Power-on reset
When power is applied to V
DD
, an internal Power-On Reset (POR) holds the device in a
reset condition until V
DD
has reached V
POR
. At that point, the reset condition is released
and the device registers and I
2
C-bus/SMBus state machine initialize to their default states.
See Section 14
for DC and AC characteristics of the POR function.
Fig 12. Write mode (output)
A5 A4 A3 A2 A1 A0 0 ASA6
slave address
START condition R/W
acknowledge
from slave
002aag833
P6 P5P7
data 1
A
acknowledge
from slave
12345678SCL 9
SDA
A
acknowledge
from slave
write to port
data output from port
t
v(Q)
P2
data 2
DATA 2 VALID
P4 P3 1 P1 P0 P7 P4 P3 0 P1 P0P6
P2
P5
t
v(Q)
DATA 1 VALID
P2 output voltage
Fig 13. Read input port register
A5 A4 A3 A2 A1 A0 1 ASA6
slave address
START condition R/W acknowledge
from slave
002aag846
data from port
A
acknowledge
from master
SDA 1
no acknowledge
from master
read from
port
data from port
DATA 1
DATA 4
P
STOP
condition